Method and system for real time characterization of soft materials and biological tissues based on nonlinear properties

ABSTRACT

Method and system for real time characterization of soft materials and biological tissues based on nonlinear properties with application in biological tissues diagnostics, robotic assisted surgery, tele-surgery, robotics and minimally invasive surgery is provided.

CROSS-REFERENCE TO RELATED APPLICATION

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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THE NAME OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The characterization of soft materials, including biological tissues, has become first priority of researchers in field of materials, biomedical, biomechanics, robotics, etc, because of the behavior complications of these materials due to nonlinearities and time dependency. Moreover, the increasing demand of interaction between these materials and non human manipulators has required efficient systems to characterize materials in the same manner of human touch. The necessity of tactile feedback in minimally invasive surgery, robotic assisted surgery and tele-surgery has been reported frequently in literatures. Robotics researchers also requested tactile sensing systems with high versatility to characterize soft objects by end effecter manipulators in order to improve the functionality of robots to interact with environment of human. In addition, diagnostic of diseases based on physical properties of tissues has been tried and failed due to lack of an efficient characterization system. Detecting lumps, tumor and studying any other disorders which effect mechanical properties of tissues require a robust system for providing possibility of their studies. To this end, the desired system not only should have the capability of touch sense of human but should be more accurate and versatile to prepare the information that human touch is incapable to provide.

2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98

Brown et al. (Lecture Notes in Computer Science, Volume 2878/2003, pp. 238-245) reported the nonlinear behavior of porcine abdominal organs in-vivo, in-situ, and ex-corpus by performing measurements while deforming the tissue by a motorized endoscopic grasper. In the absence of an efficient nonlinear viscoelasticity, analyzing time dependency of the tissue was performed through relaxation tests showing inaccurate results. To provide real behavior analyses of nonlinearities and time dependency associated with biological tissues, Shabram (“A nonlinear approach for characterization of viscoelastic materials with application in tactile sensing for robotics and minimally invasive surgery”, a thesis of MASc in Department of Mechanical and Industrial Engineering of Concordia University, Montreal, Canada, August, 2008) developed nonlinear hyperelasticity and nonlinear viscoelasticity analyses based on incremental nonlinear approach. The analytical and finite element simulations successfully confirmed the consistency of the model and method of analyses. The experimental as well confirmed the proposed model of time dependency of the material based on combination of two interactive elements within the structure of viscoelastic materials. The conclusion confirmed that the proposed model can be used for analyzing elastic/hyperelastic materials as time independent and viscoelastic/plastic materials as time dependent materials.

Based on the mentioned nonlinear approach, the method and system for characterization soft materials and biological tissues were developed in order to interact with any soft object disregarding geometry, accessibility condition and non-uniformity of behavior, and report nonlinear mechanical properties.

BRIEF SUMMARY OF THE INVENTION

The presented invention, applies the method for characterization soft materials and biological tissues by means of a system, whereas called system, which includes three main subsystems: analyzer, mechanisms and controller. The analyzer applies the method on the measurements which are taken place by mechanisms and controller enables the mechanisms to perform the deformations and measurements required in order to characterize the object by analyzer according to the method.

The system deals with soft materials/objects in general term and with biological tissues as in-vivo objects. These materials include elastic/hyperelastic and/or viscoelastic/plastic materials, which can be classified in two categories as time-independent and tine-dependent materials, respectively. Therefore, nonlinear hyperelasticity and viscoelasticity analyses are applied by the analyzer for characterizing the object and monitoring the results as mechanical properties: nonlinear elastic modulus and dissipation function of energy.

Each object regarding the accessibility condition and geometry is deformed and its behavior is measured by appropriate mechanism. Consequently, the method of analyzing is applied by analyzer according to the specific strategy developed for each mechanism.

The behavior of materials is measured by performing deformations by compressive force applied by a mechanism. The results of measurements are generally the force and displacement with respect to time. Each mechanism obtains necessary information of geometry of the object to provide the analyzer with data of nonlinearities of geometry occurred during deformation.

The mechanisms are driven by a DC servo motor which is controlled by the controller to maintain the deformation rate constant. In the presence of an appropriate control device to regulate the deformation speed, some mechanisms can be driven manually as well.

In addition to regulating the torque and speed of the motor shaft of mechanism with respect to behavior of target object, the controller prevents the object to be damaged due to deformation more than preset range and possible impact of the mechanism. Furthermore, it performs self tests and provides the user with appropriate interfaces to interact with the mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, references will now be made to the accompanying drawings, showing the way of illustration, preferred embodiments thereof, and in which:

FIG. 1 illustrates the interrelations between subsystems of the system.

FIG. 2 illustrates the drawings of top view (2A) and two sections of artificial viscoelastic object (2B and 2C).

FIG. 3 illustrates the artificial viscoelastic object without membrane (26A) lower plate with guides (26B), top plate with guides (26C), installation situation of the object on the mechanism (26D), complete artificial viscoelastic object before (26E) and after (26F) deformation.

FIG. 4 illustrates Electroforce 3200 Bose®.

FIG. 5 illustrates the schematic of interrelations of parts of Electroforce 3200 Bose®.

FIG. 6 illustrates the test results of friction of guides (6A) and spring (6B) of artificial object.

FIG. 7 illustrates the test curves of DMS-T31 with deformation speed: 2 mm/s (7A) and force-displacement curves of DMS-T31 with different deformation speeds (7B).

FIG. 8 illustrates the test force-displacement curves of DMS-T35 (8A) and force-displacement curves of DMS-T41 (8B).

FIG. 8 illustrates the test force-displacement curves of DMS-T41-2 (9A) and test curves of DMS-T41-2 with speed of 5 mm/s including relaxation (9B).

FIG. 9 illustrates the test force-displacement curves of DMS-T43 (10A) and test curves of DMS-T43 with deformation speed: 5 mm/s (10B).

FIG. 10 illustrates the test curves of viscoelastic force, HDSL and viscosity force (11A) and the curves of viscosity force with trend lines (11B) of DMS-T43.

FIG. 11 illustrates the summery of analyses of three deformation speeds for viscosity energy and dissipation.

FIG. 12 illustrates the dissipation functions of DMS-T31 (13A) and DMS-T35 (13B) with respect to deformation speed.

FIG. 13 illustrates the dissipations function of DMS-T41 (37A) and DMS-T41-2 (37B) with respect to deformation speed.

FIG. 14 illustrates the dissipation functions of DMS-T43 (15A) and dissipation functions of 5 experimental objects (15B) with respect to deformation speed.

FIG. 15 illustrates the forces of first and second deformations of a plastic object.

FIG. 16 illustrates the interrelations of parts of a general mechanism with object, controller and analyzer.

FIG. 17 illustrates the schematic of Standard clamping mechanism.

FIG. 18 illustrates the contact history of an arbitrary irregular object deformed by General clamp mechanism at time zero (4A) and t=t_(n) (4B).

FIG. 19 illustrates the deformed planes evaluation by means of contact history by General clamp mechanism at time t=0 (20A and 20B) and t=t_(n) (20C and 20D).

FIG. 20 illustrates two objects with sharp edges and sensor arrays of the clamping faces of Robust clamp mechanism at time zero (21A and 21B) and force distribution of deformation of one of the objects with concentrated stress at time t=1 (21C) and t=3 (21D).

FIG. 21 illustrates the schematic of Pre-tailored clamp mechanism with changeable clamping faces with three different objects (22A, 22B and 22C), the array of force sensors installed on fixed clamping face (22D) and the array of contact sensors installed on pre-tailored clamping faces (22E).

FIG. 22 illustrates the details of General jaw mechanism (23A) and the variation of the forces on an arbitrary object deformed by the faces of General jaw mechanism (23B and 23C).

FIG. 23 illustrates two Pre-tailored jaw mechanisms with changeable jaw faces (24A and 24B).

FIG. 24 illustrates the details of the Rigid probe mechanism.

FIG. 25 illustrates the schematic of Flexible probe mechanism (26A) and its details (26B).

FIG. 26 illustrates Flexible probe mechanism orientation with respect to the target object before (27A) and after deformation (27B).

FIG. 27 illustrates the details of Probe-jaw mechanism at displacement zero (28A) and the mechanism after achieving certain deformation (28B).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The presented invention, applies the method for characterization soft materials and biological tissues by means of a characterization system, whereas called system, which includes three main subsystems: analyzer, mechanisms and controller. The interrelations between the subsystems are shown in FIG. 1. The analyzer applies the method on the measurements which are taken place by mechanisms and controller enables the mechanisms to perform the deformations and measurements required in order to characterize the object by analyzer according to the method. Each subsystem is described separately, and, where applicable, an example of characterizing an artificial object is performed in order to present functionality of the system in practice. First the analyzer and the method are explained, then mechanisms are introduced and finally controller will follow.

Analyzer

The characterization system deals with soft materials/objects in general term and with biological tissues as in-vivo objects. These materials include elastic/hyperelastic and viscoelastic/plastic materials, which can be classified in two categories as time-independent and tine-dependent materials, respectively. Nonlinear hyperelasticity and viscoelasticity analyses including analytical, finite element analyses and experimental based on incremental nonlinear approach were presented by Shabram (“A nonlinear approach for characterization of viscoelastic materials with application in tactile sensing for robotics and minimally invasive surgery”, a thesis of MASc in Department of Mechanical and Industrial Engineering of Concordia University, Montreal, Canada, August, 2008). For describing the method the experimental is presented and described. The analytical and finite element analyses, nonlinear hyperelasticity and viscoelasticity wherever mentioned in this disclosure are referred to above mentioned reference.

Design and Fabrication of Artificial Viscoelastic Object

The viscoelastic object of the experiment is designed based on the concepts of analytical approach which is a combination of a hyperelastic material, for which a compressive spring and a membrane are selected, and a viscous media from synthetic materials with base of polydimethylsiloxane. The top view of the artificial viscoelastic object is presented in FIG. 2A. The object is designed by taking into account the available mechanism (ElectroForce®3200 of BOSE®), which applies the force only in vertical direction. To prevent the force axis from deviating during deformation, a guide mechanism was designed within structure of the object which is shown in section A-A in FIG. 2B. The guides allow the mechanism to compress the object while maintaining its vertical alignment. In this regard, four male guides 1 and female guides 2 were used to ensure that the upper plate moves vertically according to the lower plate. FIG. 2C, section B-B of the object, shows a compressive spring 3 which is placed in the center point of the plates and was centered by two small guides 4 fixed on the two plates 5 for preventing any possible buckling during deformation. An elastic balloon was used as the membrane 6 of the viscoelastic object.

The females guides were made from bronze and the male from steel which was covered by an appropriate layer of Teflon to minimize the friction. The two plates were drilled together to guarantee the centerline alignment. The female guides had a through hole, so the male could pass through the female and the upper plate. The plates were made of Plexiglas with the thickness of 6 mm. The thickness of the upper plate was sufficient to be threaded to the female guides of which the outer side had the same threads. All dimensions are in millimeter with the tolerance of ±0.5 (if applicable). The detailed photographs of the object are presented in FIG. 3A, FIG. 3B and FIG. 3C. FIG. 3D shows the object without membrane installed on the mechanism.

Finally, the object is sealed in an elastic balloon which is filled with polydimethylsiloxane. FIG. 3E and FIG. 3F show DMS-T43 before and after deformation, respectively. The Dynamic Viscosity and Kinematic Viscosity of the five different range of used polydimethylsiloxane, which are DMS-T31, DMS-T35, DMS-T41, DMS-T41-2, DMS-T43; are 971, 4865, 9740, 12175 and 29280 cP, and 1000, 5000, 10000, 12500 and 30000 cStock, respectively.

Experimental Mechanism

The machine used as the mechanism for experimental is ElectroForce®3200 of BOSE®. The machine is designed for testing materials including biological tissues. For this purpose, it is equipped, as an accessory, with hot/cold chamber to maintain the temperature and a saline bath to keep the biological materials in natural condition.

The most important features of the machine are peak force capacity: ±225N (50 lb), static (or RMS Continuous) force: ±160 N (35 lb), range of displacement: 12.5 mm (0.5 in), maximum frequency: 200 Hz, vertical test space: 0-450 mm (0-18 in), load cell space to back column: 305 mm (12 in).

The picture of the machine is shown in FIG. 4. The machine motor is a linear electromagnetic one equipped with a linear encoder placed in the upper compartment 1. The shaft of motor 2 is attached to the upper lever 3. On the lower shaft 4, a load cell 5 is installed with gain factor of 1.06 which depends on the 2.5 mV/V sensor sensitivity and, 10V excitation voltage.

The interrelation between parts of Electroforce 3200 Bose® is presented in the FIG. 5. The controller parameters are set by the user and the motor activation occurs due to these parameters. When the motor shaft compresses the specimen, the reaction of the specimen slows down the shaft movement. The feedback from load cell and encoder are used by the controller to regulate the motor shaft movement for complying with these parameters.

Tests on the Spring and Guides Friction of the Viscoelastic Object

The tests procedure is as follows: 1—The viscoelastic object is assembled without spring and elastic membrane for measuring the friction of the guides. The results are presented in FIG. 6A which shows the force and displacement with three ranges of speed: 1 mm/s, 2 mm/s and 5 mm/s. 2—Following the above, the spring is tested without the guides. Therefore, the force and displacement are related to the spring alone. The results are shown in FIG. 6B. It is shown that the spring has a linear behavior with stiffness of 0.52 kN/m. 3—The guides, elastic membrane and spring are then assembled.

The viscoelastic object is filled with one of five grades of polydimethylsiloxane. It is tested three times with every deformation speeds which are 0.1, 0.2, 0.4, 1, 2, 5 millimeter per second. Then, the membrane of the object is torn up and the structure of the object is cleaned completely. Another membrane is installed and filled with another range of polydimethylsiloxane. In such a way, five artificial viscoelastic objects are provided and tested. Any of these objects has a different membrane and viscous media but all of them use the same spring, guides and structure. The upper shaft of the test machine is set to a precise position which guarantees equal space between two plates for all of the objects. Therefore, we have five different objects with same spring, guides' friction and different membrane, which constitute different hyperelastic element for each object; however the only difference is the membrane, and different viscous media. In other words, five objects are the same except membrane and viscous media. Although, it seems that only two elements are different but these are the most significance elements for viscoelastic material behavior because these two elements are interactively responsible for time dependency of viscoelastic material. Accordingly, other differences are produced by differences in these two elements: 1—Less viscous media is filled more easily and provide more volume for filing by deforming the membrane during the filling due to gravity, which is more significance than viscosity adhesion. On the contrary, more viscous media takes less room due to construction of strong bonds between membrane and structure. 2—Less viscous media provide more body force during deformation which cannot be neglected during high speed deformation. 3—The membranes are not the same, though they have been selected from one pack, from the same size, model and material of balloons. 4—During installation the structure inside the membranes, they go under tension which is not by any means calibrated and results in different resistance of the membrane. The kinematic viscosities of the viscous media are in ascending manner: 1000, 5000, 10000, 12500 and 30000 cStock.

Test Procedures and Results

The test began with Polydimethylsiloxane DMS-T31. The motor speed was set at 0.1 mm/Sec. and maximum displacement to 10 mm. The data of load and displacement with respect to time were obtained. Afterward, the experiments with speed of 0.2, 0.4, 1 and 2 mm/s. were achieved. FIG. 7A shows the experiment with speed of 2 mm/s. The vertical axis corresponds to axial efficiency 1, force 2 and displacement 3, respectively, in ascending order; and horizontal axis corresponds to time.

The tests with higher speeds were performed and the results are presented in FIG. 7B. As it is shown, the loads increase with respect to speeds of deformation. It should be noted that the curves of 0.1, 0.2, 0.4 and 1 mm/s are very close in a manner as it can be concluded that regarding the structure, this object is not sensitive to rate of deformation up to a certain speed. In other words, up to a certain deformation speed, the object is time independence or hyperelastic and beyond this speed it shows viscoelastic characteristic and time dependency. By observing the curves of deformation speed of 1 and 2 mm/s, it can be seen that from 0 to 5N both curves are matched that indicates that up to point A, the object is showing time dependency while it does not differ between two different deformation speed. In addition to that, it can be seen that the difference between the two curves is increasing with the increase of deformation. This confirms that the viscoelastic behavior is not only the result of presence of viscous media but also the interaction of viscous media with hyperelastic element or precisely with structure of the object. It should also be noted that machine performance in few first moments of deformation with high speed can be differed from preset parameters because the control system encounters significance delay for adjusting the motor torque with behavior of the object under desired speed. The performance of the machine can be verified by investigating the efficiency line of FIG. 7A.

After having cleaned the structure of the object from DMS-T31, another balloon is installed and filled with DMS-T35. The tests were performed with deformation speed of 0.1, 0.2, 0.4, 1, 2, and 5 mm/s and the results are presented in FIG. 8A. As it is shown, the loads are increasing a little (2N) from 0.1 mm/s to 5 mm/s deformation speed. If we neglect oscillating behavior due to body force of the viscous liquid, it can be concluded that all curves are close to each other except last half of the curve of 5 mm/s. Consequently, this object is not much viscoelastic comparing to its hyperelasticity. In other words, though it contains a viscous liquid with higher viscosity, it shows very little viscoelasticity. Evidently, both object of DMS-T31 and DMS-T35 have same spring, guides and structure, and the latter is even more viscous. Obviously, the membrane is the reason for the difference. By comparing the curves of FIG. 4-8 and FIG. 4-9, it can be seen that the highest force due to hyperelasticity at the last step of displacement for DMS-T31 is 15N and for the same point on the curve of DMS-T35 is 25N. In addition, the highest force due to hyperelasticity and viscoelasticity of DMS-T35 is 20N which is less than the force due to hyperelasticity of DMS-T31. Therefore, it can be concluded that the membrane is very tight in object DMS-T35. In other words, the membrane is too hard to allow the viscous liquid deform it. Consequently, the liquid is compressed in a manner that no velocity profile is produced during deformation. Once more, it is confirmed that the structure of the object is as important as the properties of constructive elements of a viscoelastic material for its behavior with respect to time.

The other characteristic of the objects DMS-T31 and DMS-T35 is the oscillation behavior after 30% of the total deformation (3 mm out of 10 mm displacement). It can be concluded that the body force cannot be completely neglected when deformation occurs in dynamic manner.

The tests with DMS-T41 were achieved and the results are presented in FIG. 8B. As it is shown, the curves of deformation with speeds 0.1, 0.2 and 0.4 mm/s are very close to each other and for second half of the deformation even close to curve of speed 1 mm/s. The curves of 2 and 5 mm/s are clearly higher than the others.

The tests with DMS-T41-2 were performed and the results are presented in FIG. 9A. As it is shown, the results are consistent with the results of DMS-T41.

Since the behavior of the test of the object DMS-T41-2 was smooth, the relaxation test was achieved with speed of 5 mm/s. According to definition of relaxation test, the object was deformed to 10 mm then the upper shaft was fixed. The curves of load 1, displacement 2 and efficiency 3 are shown in FIG. 9B. As it can be observed, the compressive load is increased up to 24.2N then the load is decreased to 15.8 after having fixed the shaft for 3 seconds. More precisely, the load is decreased from 24.2 to 16.6N in half second and slowly is decreased to 15.8 in in 2.5 seconds. It can also be observed that the efficiency of the machine during the 0.1 second of the start point was deteriorated from the set point. This happens when the delay of respond of the control system is greater than the response of the material. In another word, the system has a certain delay to adjust the load for maintaining the preset velocity of deformation.

The tests with DMS-T43 were achieved and the results are presented in FIG. 10A. As it is shown, results are very similar to the results of the object DMS-T41-2, though its viscosity coefficient is more than twice of the latter. It can also be observed that the oscillation behavior is considerably decreased. It is again confirmed that interaction between the elements of a material is the most important factor for viscoelastic behavior.

The curves of load, displacement and efficiency of testing object DMS-T43 with speed of 5 mm/s are shown in FIG. 10B. It can be seen that the efficiency in the 0.3 second of the test time is considerably deteriorated due to machine performance regarding the delay of control system to adjust the torque of the motor with behavior of the object.

As it was shown, the experimental confirms that the model of a viscoelastic material as an interactive combination of a hyperelastic element and viscous media is consistent with behavior of real viscoelastic materials.

Experimental Outcome

Having performed experimental, it is necessary to make a summery to finalize general solution strategy for characterization procedure: 1—Soft materials can be classified mainly as hyperelastic and/or viscoelastic materials. 2—The time dependency of viscoelastic materials is due to the presence of a liquid or semi liquid media which absorbs the energy by internal friction. 3—The viscoelastic material is subjected to a large deformation which requires the presence of a hyperelastic element in its structure. 4—Viscoelastic behavior is the result of interaction of two elements with characteristic of hyperelasticity and viscoelasticity in certain conditions. 5—For every viscoelastic material, there is a limit of deformation speed up to which time dependency behavior is insignificant.

Method

Based on the outcome of experimental, analytical concepts and finite element simulation results, the method for characterization of soft materials especially biological tissues in-situ and in-vivo is built. Since the analytical and simulation assumptions are idealistic which cannot be provided in real condition and the experimental subjects are real objects—though they are artificial—the solution is based on the experimental results. As it was mentioned that a viscoelastic material consists of two elements with different behavior characteristics, it is required that the object to be presented with two properties which are generally nonlinear. To this end, the behavior of the object is divided in two behaviors: time dependent and time independent. It should be taken into account that the elasticity modulus of a hyperelastic material can be only presented by a curve of stress-strain as a nonlinear property of a nonlinear behaving material. Therefore, a number as elasticity modulus cannot be valid unless the range of deformation could be considered in the linear range that is not the case of large deformation of hyperelastic material including biological tissues.

According to the curves of five tested objects, there is a limit of speed of deformation that the object behaves independent of time as a hyperelastic material, which is, whereas, called hyperelasticity deformation speed limit (HDSL). This speed deformation limit is 0.4 mm/s for DMS-T31, DMS-T41, DMS-T41-2, DMS-T43 and 1 mm/s for DMS-T35 (see FIG. 7B, FIG. 8A, FIG. 8B, FIG. 9A and FIG. 10A). Therefore, one curve in this range of deformation speed is used to calculate the nonlinear elastic modulus as it was discussed in nonlinear hyperelasticity. For viscoelasticity property, the relevant curve of force at the specific deformation speed which is in the range of time dependency; i.e. above the hyperelasticity speed limit is subtracted by the curve of hyperelasticity deformation speed limit (HDSL). The result is another curve which represents the force absorbed by the viscous media during deformation. FIG. 11A shows the curves of DMS-T43 including HDSL; viscoelastic curves of 1, 2 and 5 mm/s, and viscous force resulting from curves of 1, 2, 5 mm/s deformation speed. Consequently, the resulted curves are viscosity force curves, which are used for characterizing viscoelasticity property. In this regard the area under the curves of force-displacement is calculated which is the work or energy absorbed by viscous media. For simplicity of the calculation, the trend line of each curve is drawn and shown in FIG. 11B. By calculating the area enclosed between the trend line and horizontal axes, total energy absorbed by the viscous media during deformation is obtained. The average of dissipation of each deformation speed according to equation 43 is the result of the energy divided by time. The viscosity energy and average dissipation for five objects according to deformation speed are summarized in FIG. 12.

By drawing the curves of dissipation with respect to deformation speed, the viscoelastic behavior of each object can be characterized. The FIG. 13A, FIG. 13B, FIG. 14A, FIG. 14B and FIG. 15A show the dissipations of five objects with respect to deformation speed. Each curve is presented with trend line and polynomial trend curve for facilitating the study of viscoelastic behavior of the objects with respect to deformation speed. It can be seen that the curves of dissipations with respect to deformation speed is more likely comply with polynomial function with degree of two as it could be predicted according equation 35. Therefore, characterization of viscoelasticity of object requires at least three points on the curve of dissipation. FIG. 15B shows the dissipation of five objects together on one chart. It can be seen that the viscoelasticity of the objects decrease in descending manner DMS-T41, DMS-T43, DMS-T31, DMS-T41-2, DMS-T35 while the viscosity of the viscous media is 10000, 30000, 1000, 12500 and 5000 cStock, respectively. This confirms again that viscoelasticity is a property dependent on the interactive correlation of consisting elements of an object. Therefore, the general solution for characterizing a viscoelastic object is: 1—deforming the object and measuring the force and displacement with respect to time with four deformation speed; one as HDSL and three higher than HDSL, 2—calculating the hyperelasticity as a function of stress-strain, 3—calculating dissipation function with respect to deformation speed.

Since elastic and hyperelastic materials are time independent, the second deformation curve with high speed coincides with the curve of low speed deformation. First and second deformations of viscoelastic materials were discussed in detail, therefore, the behavior of plastic material should be clarified. A plastic material behaves like an elastic material until certain limit and then yields and flows; therefore, the reaction is the resistance of semi solid flowing. Consequently, the reaction force stays almost constant during deformation. FIG. 16 shows an example of behavior of a plastic material during first and second deformation with low and high speed deformation, respectively. In other words, plastic object can be treated like a viscoelastic object with the lack of a hyperelastic element. A plastic material also absorbs energy during deformation in the same manner of viscoelastic material but in viscoelastic material, part of the energy of deformation is stored by hyperelastic element which causes the return of the object to the first configuration in a certain period of time. Plastic material absorbs all the energy and waste it by the internal friction, therefore, it remains stable at the final configuration with the balance of total energy.

Having explained the characterization procedure for viscoelastic and plastic objects, it is essential to consider the circumstances on which characterization method is applied. The characterization system or any tactile sensing system has two duties to accomplish: characterizing soft materials qualitatively and quantitatively. The soft materials can be classified as: elastic materials, hyperelastic materials, viscoelastic materials, plastic materials and combinations of them. For performing the task of characterization qualitatively and quantitatively, at least two deformations with two different speeds are required. The first deformation with low speed in the range of HDSL results in characterization of material elasticity, hyperelasticity or plasticity quantitatively and second time deformation with high speed to: 1—confirm the quality of the object whether to be elastic or hyperelastic, 2—confirm the quality of the object whether to be plastic and characterize its plasticity quantitatively or 3—confirm the quality of the object whether to be viscoelastic and characterize its dissipation quantitatively at the deformation speed. In other words, first deformation with low speed characterizes the elastic or hyperelastic element of the object. Second deformation with high speed characterizes the other element of the object if it exists. Though for a complete characterization of a viscoelastic object, four deformations with different speeds are required, second deformation is sufficient for most of applications.

Mechanisms

Having discussed the method and strategy of general solution which is performed by analyzer, the mechanisms are disclosed which performs the required deformations and measurements for any object in any configuration and any orientation including biological tissues in-situ and in-vivo. The specific procedure of each mechanism is also explained accordingly.

The characterization of materials is performed by deformation occurred by a compressive force and measuring the force and displacement with respect to time. In this regard, the target object is deformed by one of the mechanisms depending on the accessibility condition, contour of the object, concentration of stress, etc. Each mechanism uses its own specific control and analyzing method.

The diagram of a general mechanism of the system is shown in FIG. 17. The object is touched and deformed in one direction by means of a motor's shaft. The reaction force by the object is measured by the load cell. The displacement rate which is the result of the deformation of the target object is measured by an encoder. A contact sensor records the time of touch, force and displacement measurements. These measurements, which conform the functions of force and displacement with respect to time, are sent to analyzer.

The deformation rate is required to be in constant manner in order to allow the analyzer calculate the properties of the target object. Therefore, the controller regulates the speed of motor's shaft in order to maintain a constant displacement speed during deformation according to the behavior of the target object. For this purpose, the outputs of force and displacement sensors are sent to the controller, which regulates the speed and torque of the motor's shaft.

Standard Clamp Mechanism (SCM)

This mechanism grasps the object by means of two parallel clamping faces. Consequently, it is used for the objects with two parallel accessible surfaces. This mechanism is similar to typical test machines for elastic material characterization while the material behavior is within the linear range. SCM performs the characterization of the target object in the similar manner with several differences, e.g., nonlinear analyzing methods are applied to obtain nonlinear properties of the materials.

FIG. 18 shows the standard clamp mechanism (SCM). The mechanism applies the compressive force by two parallel clamping faces. One clamping face is fixed 1 and the other one 2 is driven by a DC motor 3. The driving shaft 4 of the motor is attached to a linear encoder 5 which measures the displacement of the shaft. The fixed clamping face is supported with a bar which is equipped with a load cell 6. The moving clamping face is equipped with a contact sensor 7. When the contact sensor touches the contour of the object 8, the time is set to zero. Eventually, the force and displacement sensors are synchronized for the zero level at the touch of the object. The result is the continuous functions of force and displacement with respect to time.

For characterizing the object by SCM, it is assumed that initial touched surfaces of the object remain unchanged during deformation. In another word, not only the deformation is taken place with reserving volume but also the contact surfaces are as well unchanged. Another assumption makes the necessity that the object to be isotropic; i.e. the properties of the material should be uniform and free of direction. The analyzer takes advantage of these assumptions in order to calculate the initial and final configuration in every time steps of the object to be used for determining its properties. Controller regulates the drivers torque in order to maintain constant deformation speeds.

Procedure of Analyzing for SCM

Since this mechanism is standard, the analyzing strategy can be considered a standard procedure. Therefore, for other mechanisms only the differences will be discussed.

The solution procedure for SCM is: 1—Setting first deformation speed and displacement limit, e.g. 0.2 mm/s and 5 mm. 2—Setting force limit for the object, e.g. 30N. 3—Starting deformation. 4—Recording the time and displacement at the touch point of the object by the contact sensor, e.g., 1.5 s and 1.2 mm. 5—Recording the force with respect to time and to displacement. 6—Retracting the moving clamp and wait for the object to return to the stand status. 7—Analyzing the results according analysis of nonlinear hyperelasticity. 8—Monitoring the curves of force-displacement, stress-strain and elastic modulus-strain. 9—Setting second deformation speed, e.g., 3 mm/s. 10—Starting deformation. 11—Recording time and displacement of the touch point by the contact sensor. 12—Recording force with respect to time and displacement. 13—Retracting the moving clamp. 14—Analyzing the quality of the object, e.g., hyperelastic, plastic, etc. 15—Monitoring the curves of first and second deformation of force-displacement. 16—Concluding the quality of the object by comparing two curves of step 15. 17—Monitoring the properties of object whether it is elastic or hyperelastic, curves of stress-strain and modulus-strain; whether it is plastic, curve of stress-strain and dissipation at the deformation speed; whether it is viscoelastic, curve of stress-strain at the low speed and dissipation at the high deformation speed. 18—Calculating two other deformation speeds if complete characterization of the dissipation function of viscoelastic object, if exist, is required and repeating step 9 to 17.

General Clamp Mechanism (GCM)

FIG. 19A shows the clamping faces and the object of General clamp mechanism; the other parts of the mechanism are similar to the parts of SCM. The object 1 is grasped by fixed clamping face 2 and moving clamping face 3. This mechanism is used when the target object has access from two opposite sides but does not have regular profile of surfaces to comply with clamping faces. As a result, one contact of the object does not provide enough geometry information to be used for evaluation of its volume, which is necessary for determining the properties of the object. Therefore, the clamping faces are equipped with arrays of contact sensors 4. When the faces touch the object respective points of touch trig the sensors 5 and map the profile of the object's surface at the time zero. Along with deformation, the changes of geometry bring other contact sensors in touch with the object. Thus, the deformation history and contact history of the object provide data for the analyzer to evaluate deformed volume with respect to time. In other words, the analyzer evaluate the geometry of the object with respect to time. time FIG. 19B shows the contact history of the irregular object deformed by GCM at time t=t_(n). As it is shown, the irregular geometry of the object leads to irregular deformation considering that the deformation is assumed uniform. The analyzer uses these data to calculate the distribution of the deformation rate and force within the volume and nonlinear properties of the object.

Procedure of Analyzing for GCM

GCM solution strategy is similar to SCM with the exception that the geometry of the object is not known. Therefore, the volume of the object which is deformed due to the compressive force is unknown. In this regard the array of contact sensors are provided with the clamps to map the topography of the object during deformation. By dividing the volume of the object to planes and using relevant contact sensors for each time step, the topography of the object in plane and consequently in 3D is evaluated. FIG. 20A shows the procedure of evaluation of the volume in plane indicated with a flesh (j=6) at the time zero. FIG. 20B shows the evaluated volume by the analyzer at time zero. The object 1 is deformed by fixed clamping face 2 and moving clamping face 3. The untrigged contact sensors 4 are identified from trigged contact sensors 5 by analyzer. FIG. 20C and FIG. 20D show the evaluation procedure for the same object at the time step t_(n). In other words, for each contact sensor at any time there is an output of zero or one which refers to intrigued and trigged status, respectively. Therefore, the status of each contact sensor is a function of position and time which returns zero or one, i.e., f_(m)(i, j, t)=0 or f_(f)(i, j, t)=1; where f_(m) is the function relevant to moving clamp, f_(f) is the function relevant to fixed clamp, i is the number of row, j is the number of column of the array and t is time. Consequently, the procedure of GCM has an extra step, i.e., 6a, after step 6 and before step 7 for calculating the geometry and volume of the object as functions of time involved in the deformation during time interval to be used for step 7.

Robust Clamp Mechanism (RCM)

When the shape of the target object provides non-uniform deformation due to sharp edges and concentrated stresses, GCM leads to certain errors. This is because that the distribution of force cannot be sensed by one single load cell. In this regard, robust clamp mechanism is designed which is shown in FIG. 21A and FIG. 21B. The mechanism is equipped with arrays of force sensors 1 on both fixed clamping face 2 and moving clamping face 3 in addition to contact sensors. When the object 4 is touched by the mechanism, the contrast of trigged contact sensors 5 and unrigged contact sensors 6 map the surface of the object with contact with the mechanism. Therefore, not only the geometry of the object is evaluated during deformation also the concentration of stress within the volume of the object is calculated by using distribution of force measured by force sensors. Characterization of such an object results in properties as functions of space status, i.e. geometry, material and load. The contact sensors are used provided that the threshold of force sensors are not appropriate for measuring contact history, otherwise, instead of contact sensors, force sensors are used to increase the resolution. The other parts of the mechanism are the same of SCM.

Procedure of Analyzing for RCM

Analyzing procedure of RCM is similar to GCM with the difference that the assumption of uniform distributed force on the clamp cannot be applied due to geometry of the object which creates the concentration of stress in some part of the object. In this regard, the array of force sensors within the clamps faces provides the information of distributed force on the faces quantitatively. Therefore, another function in addition to contact sensors function, is created by measuring the force of every single force sensor in every time step of analysis, i.e., F₁ (i, j, t)=f N. The analyzer uses the pattern of force sensors and contact sensors in order to calculate the deformation performed within the entire evaluated volume of the object. FIG. 41A and FIG. 41B show the function of force sensor array at time 1 and 3 of deformation for one of the objects. Consequently, the procedure of RCM is similar to GCM but the solution of the step 6a between step 6 and 7 of SCM is more complicated and the function of force array instead of load cell output is used for analyses.

Pre-Tailored Clamp Mechanism (PCM)

The FIG. 22A, FIG. 22B and FIG. 22C show Pre-tailored clamp mechanisms according the profile of different objects. This mechanism has the same characterization of GCM, except that the fixed clamping face 1 and moving clamping face 2 are changeable according to the contour of accessible surfaces of the target object 3. Deformation is performed by the driving shaft 4 of a DC motor 5 and displacement is measured by an encoder 6. The force is measured by both load cell 7 and the force sensors of the array installed within fixed clamping face.

The array of fixed clamping face is shown in FIG. 22D. The fixed clamping face 1 is equipped with array of force contact 2.

FIG. 22E shows the pre-tailored clamping faces 1 equipped with array of contact sensors 2. Consequently, each mechanism uses three array of sensors: one array of force sensors within fixed clamping faces under the lower pre-tailored clamping face and two array of contact sensors within two pre-tailored clamping faces touching the target object. The mechanism functions in the same manner that GCM does while the pre-tailored clamping faces allow the mechanism to obtain more precise data from the object during deformation. In addition, this mechanism provides the possibility for testing and characterizing objects with specific manners of loading and deformation. In other words, not only the properties of the object which is dependent on the materials disregarding its geometry, but also the behavior of any object, which is function of material, geometry and loading, can be determined by this mechanism. One of the advantages of this mechanism is the possibility of testing the objects which might be damaged by significant deformation. For overcoming the difficulty of defining the concentration of stress in the object, the fixed clamping face is equipped with an array of force sensors (gauges) to provide force distribution during deformation. Therefore, the behavior of the object, that may be non-uniform within the volume, can be characterized by the analyzer.

Procedure of Analyzing for PCM

The procedure for analyzing an object with PCM is completely similar to RCM but in this case the object geometry is known and volume of the object is not required to be calculated by preparing the pattern of contact and force sensors. Since the concentration of the stress can be evaluated by only one array of force sensors, the calculation of the step 6a is more similar to GCM rather than RCM. On the other hand, the hyperelasticity should be computed as RCM by taking into account the distribution of the force on the object surface. It should be taken into account that PCM is used for specific objects including biological organs; therefore, the deformation is more limited than other clamp mechanisms.

General Jaw Mechanism (GJM)

The details of GJM are shown in FIG. 23A. This mechanism applies the compressive force to the target object 1 by means of two hinged faces which conform a jaw. The faces of the jaw are equipped with force sensors 2 and contact sensors 3. The mechanism uses an angular displacement sensor (encoder) 4 for measuring deformation. In addition to force sensors on the jaw faces, the mechanism uses another force sensor 5 on the driver levers. The torque and speed of the motor 6 which applies the force to the jaw is regulated by controller, though the jaw mechanisms may be driven manually provided that a device controls and provides different constant angular speed of deformation. In this case, the user should be aware of limit of applied force in order to prevent any possible damage to the object. In case of sensitive force sensors with low threshold, the contact sensors can be replaced with force sensors.

Thus, during deformation, force sensor of driver's shaft provides the data of total applied force and regulate the driver's torque within the limits range of force prescribed for the object. Since the deformation of the object in a jaw does not comply linearly with angular displacement, contact surface of the object is varying while the directions of the forces are continuously changing with respect to the axes of the object. Therefore, the force sensors embedded in the jaw's faces are required to synchronize the forces on the objects with the total sensed force by motor shaft's sensor. In other words, the contact force on the object of any point of contact is result of friction force which is applied along with face of jaw and reaction force which is perpendicular to the jaw's face. These forces are varying in magnitude and direction with respect to the last deformed configuration. FIG. 23B and FIG. 23C show the variation of the reaction forces 1 and friction forces 2 on an object 3 deformed by the faces of general jaw mechanism.

One of the most important advantages of this mechanism is the capability to be integrated with end effectors of robots and minimally invasive surgery tools.

Procedure of Analyzing for GJM

Analyzing procedure of GJM is the same as GCM with the exception of coordinate system for solving the equations. GCM analyzer uses Cartesian coordinates system and deformation is taking place in longitude while GJM analyzer uses cylindrical coordinate system and deformation is angular. Therefore, the deformation speed is considered as angular velocity and is measured in rad/s.

The arrays of force and contact sensors provide the information about object geometry during deformation as functions of time. Therefore, the mechanism can grasp any object provided that the faces of jaw apply considerable friction force to maintain the object between the jaws during deformation. To this end, the faces of jaws are equipped with tooth to hold the object in contact with mechanism. If any slip happens, the contact sensors are able to detect it. In case of occurrence of any slip, the grasping should be repeated.

Pre-Tailored Jaw Mechanism (PJM)

This mechanism functions in the same manner of GJM but the faces of the jaw are changeable with pre-tailored faces with regular curved cross sections. FIG. 24A and FIG. 24B show two PJM changeable jaws. The faces are equipped with contact sensors 1 to trace the deformation of the object during deformation. On each lever of jaw a force sensor 2 is installed to measure applied force. Each lever is provided with a connection 3 for fixing the changeable jaws. Similar to GJM an encoder 4 measures the angular displacement. This mechanism is used when the contour of the target object 5 is curved.

Procedure of Analyzing for PJM

PJM contrary to GJM is designed for characterizing the object with known geometry. Though these objects can be sensed precisely by GJM, it requires that the objects undergo certain deformation which might be out of their allowable range. Also prevent this mechanism concentrated deformation on the objects due to conformity of the jaw's profile with object's contour. Moreover, it provides deformation on the objects which have very thin and fragile skin and may fail to deform under GJM. Finally, it can deform the objects without friction required between the jaw's face and contour of object by using GJM. It should be mentioned that the profile of the jaw is not required to be at the same curvature of the object, because the contact sensors installed on the jaw's faces provide the information of the geometry of the object during deformation. Therefore, the procedure of the analyzer of this mechanism follows the procedure of analyzer of PCM with consideration of using cylindrical coordinate of GJM.

Rigid Probe Mechanism (RPM)

The characterization of an object with one access surface is impossible by using clamp or jaw mechanisms because these mechanisms require two access surfaces in order to touch and apply force to the object. In this regard, probe mechanism is designed to characterize the properties of the target object by applying compressive force on one access surface of the object with assumption that the opposite surface of the object is fixed.

FIG. 25 shows the RPM. The mechanism uses a probe 1 to deform the target object. The probe is pushed by a linear motor 2 of which the shaft is attached to a linear encoder 3. The force is transmitted by a rigid rod 4 which passes through a solid tube 5 and rigid guide 6. The probe is provided with a load cell 7 which measures applied force to the object. On the head of the probe, a contact sensor 8 is installed. At the time of touching the object by the probe, the contact sensor is trigged and records the time for which the functions of force and displacement are set to zero. Since during the characterization of the object by probe mechanism, the thickness of the object is unknown, an ultrasonic thickness meter is provided of which emitter 9 and receiver 10 are installed on the probe head. When the probe touches the object and is securely in contact of the surface of the object, the controller initiates the meter to measure the thickness of the object, which will be used by analyzer for calculating the properties of the object.

The deformation is taken place twice with low and high deformation speed, unless more deformation are required, in the same manner of other mechanisms. The controller regulates the deformation speed by adjusting the torque of the motor with respect to the behavior of the object.

The present mechanism is suitable to characterize the object in-situ and iv-vivo with limited access. They can be integrated with endoscope or being used with endoscope for minimally invasive surgery and with special robots used for robotic assisted surgery.

Flexible Probe Mechanism (FPM)

This mechanism functions in the same manner of RPM. In addition, the body of the mechanism is flexible to be used in narrow spaces. FIG. 26A shows the schematic of FPM. The details of FPM are shown in FIG. 26B. The probe mechanism consists of a flexible tube 1 which can be easily maneuvered to the target object's surface by passing through holes and narrow channels. At the fixed end of the tube a linear motor 2 equipped with linear encoder 3 is installed. A flexible rod 4 is passed through the flexible tube and is attached from one side to the shaft 5 of the linear motor, and from other side to the rigid piston 6. The surface of the rod is covered by graphite in order to minimize the friction between the rod and the tube. At the free end of the tube, a rigid shallow cylinder is installed in a manner that provides a rigid guide 7 for the rigid piston to slide freely without deviation from longitude axis. A load cell 8 is attached to the free end of the piston. A cap is installed on the head of the piston which is equipped with a contact sensor 9.

The flexible tube is provided with eight longitude holes in its wall. Four of the holes are the guides for steering wires 10 which are used to steer the tube to the desired position perpendicular to the object surface with minimum gap in order to maximize the deformation range by means of steering levers 11. The other four holes are equipped with four longitude resistive sensors. These sensors are sensitive to longitude deformation. When the tube is curved upward, upper sensor is compressed and its resistance is decreased and the sensor in below is stretched and its resistance is increased. The holes of resistive sensors are arranged on the quadrants of a cycle. Therefore, the final position of the free end of the tube can be obtained during deformation by the difference of sensors outputs.

The tube is driven by the steering levers and is locked to the desired position at the target object. The motor shaft pushes the piston perpendicular to the object's surface and pulls it back when the deformation is achieved. The object is deformed by the probe's head 12 while the linear encoder measures the displacement and load cell measures applied force to the object with respect to time of which reference is set by contact sensor.

The deformation of the locked tube during the deformation of the object is calculated by the longitude resistive sensors. More precisely, the change of head position of the mechanism during deformation due to the reaction of applied force is measured by resistive sensors. In this manner, the real deformation of the object with respect to time can be calculated at any time. Similar to other mechanisms, the displacement and force functions with respect to time are provided for analyzer to calculate and display the properties of the object. The orientations of the probe relative to the object before and after deformation are shown in FIG. 27A and FIG. 27B, respectively.

Since during the characterization of the object by probe mechanism, the thickness of the object is unknown, an ultrasonic thickness meter is provided of which emitter 13 and receiver 14 are installed on the probe head. When the probe touches the object and is securely in contact of the surface of the object, the controller initiates the meter to measure the thickness of the object, which will be used by analyzer for calculating the properties of the object.

The deformation is taken place twice with low and high deformation speed, in the same manner of other mechanisms. The controller regulates the deformation speed by adjusting the torque of the motor with respect to the behavior of the object.

The present mechanism is not only suitable for being integrated with endoscopic apparatus but also can be used to diagnose the internal tissues of which mechanical properties are changed under effect of tumor, cancer, infection, etc. The mechanism can be used for robotic assisted surgery and tele-surgery as well as for special robots. The mechanism can be also used to diagnostics of disorders such as: fibrium, miium, ectopic pregnancy and retained placenta.

Jaw-Probe Mechanism (JPM)

Jaw-probe mechanism is a combination of jaw and probe mechanisms. Since in some circumstances, like inside pipes, narrow channels, stomach, etc., the probe mechanism cannot be appropriately maneuvered, the JPM is designed to overcome the difficulty of accessibility through narrow spaces. FIG. 28A shows the details of JPM. The mechanism uses a piston-cylinder 1 for transmitting the force from jaw to the probe and another piston-cylinder 2 for maintaining the vertical alignment of the probe 3. As other probe mechanism, PJM uses an ultrasonic thickness meter to measure the thickness of the object. The emitter 4 and receiver 5 are installed on the surface of the probe besides a contact sensor 6. The force sensors 7, on this mechanism, are installed on both jaw levers: on the driving lever for measuring the applied force and on the base lever for controlling smoothness of the movement of the probe. An encoder 8 measures the angular displacement which is converted to linear displacement by the analyzer. FIG. 28B illustrates the mechanism after having achieved a certain deformation.

Procedure of Analyzing for RPM, FPM and PJM

The procedure which the analyzer of RPM uses is the exact procedure of SCM. The only difference is that the analyzer uses the output of ultrasonic thickness meter for complete the data of geometry of the object before starting any analysis. All probe mechanisms function in the same manner and their difference is the condition of accessibility of the object. For this reason the probe mechanisms are appropriate mechanism for using on biological tissue by minimally invasive and robotic assisted surgery. All probe mechanism are equipped with four more contact sensors on the quadrant of a cycle to record the touch time for controlling the perpendicularity of the probe with the surface of the object. Thus simultaneous touch time of four contact sensors means that the probe is perpendicular to the object; otherwise the deviation is measured with the difference of touch time of the sensors at the other side of the probe.

Pre-Tailored Probe Mechanism (PPM)

PPM is a combination of PCM and RPM. The structure of PPM is the structure of RPM but the probe is replaced with pre-tailored face on which several probes are installed and function in the same manner of a single probe. In other words, the PPM is combination of several RPM which are arranged according to contour of objects surface. The pre-tailored clamp consisting probes is driven by one single motor and displacement is measured by one linear encoder. This mechanism is appropriate for lump and tumor detection. Each probe is equipped with an independent ultrasonic thickness meter. The mechanism

Self-Tailored Probe Mechanism (SPM)

SPM is a combination of GCM and RPM. The RPM are arranged on a 2D array. At the adjacent of the target object, perpendicular to the surface of the object, the mechanism initiate the motor of each individual probe with low speed until each one touches the surface of the object where the motor is stopped and the position of the probe and consequently the geometry of the object relative to the position of the individual probe on the array is recorded. When all individual probes touched the surface of the target object, the mechanism initiate the procedure of characterizing the object by performing the deformation by all probes synchronized with the same speed. Each probe is equipped with an independent ultrasonic thickness meter. In other words, the mechanism is the combination of several RPMs which are arranged in a 2D array.

The analyzer combines the results of all probes and provides a complete characterization of the object including the undeformed geometry of the object.

Procedure of Analyzing for PPM and SPM

the procedure of PPM and SPM is similar to RPM with few differences. Any individual probe of these two mechanisms is analyzed according to the procedure of RPM but their results are combined by analyzer for the complete characterization.

Controller

Controller plays a very important role in the performance of the system. The major duties of the controller are: 1—Regulating the torque and speed of the motor shaft according the behavior of the object and preset parameters such as deformation speed via the motor's driver. 2—Control the torque and displacement of the shaft within the limits of the allowable range preset by user according the target object such as limit of applied force and displacement. 3—Regulating the speed of the motor shaft before the contact of the mechanism with the object in order to prevent any effect of impact. 4—Apply appropriate procedure of deformation and analyzing method according to each mechanism. 5—Providing the facility for user to interact with the system. 6—Performing the self test and control the performance of the system regarding the procedure and support the user with appropriate feedbacks.

Since the deformation is required to be performed with preset deformation speed, the torque of the motor should be regulates according the resistance of the object against the deforming force. To this end, the controller uses the output of the encoder and calculates the speed of deformation, then compares it with the desired one. Consequently, the controller performs the compensation the error by increasing or decreasing the power of the motor in order to maintain the speed of deformation constant. For this purpose, the controller uses PID method for the first deformation. For the second deformation, the controller takes advantage the pattern of the first deformation to regulate the motor's torque with less error and more precision.

Soft materials, especially biological tissues may be damaged due to extra load or deformation. Therefore, the limit of force and displacement of the motor shaft is preset by the user within the secure range. The controller applies a safe margin to stop the motor before reaching to the secure limit of load or displacement.

An impact of the mechanism of the system with the object with speed more than a certain limit may cause damage to both, the mechanism and object. The controller drives the motor shaft very slowly during the first deformation and records the position at which the contact has occurred. For the next deformation, the controller regulates the speed of the shaft very slowly until the touch point and then start to drive it at the preset speed.

Depending on geometry, accessible surface and certain conditions, the sensing and characterization of objects should be performed by appropriate mechanism. The procedure of deformation for each mechanism is conducted and followed by controller.

For initiating the sensing and characterization process, the parameters of the system function should be set. This task is achieved by controller by providing human-machine interface. In addition, the controller records the data in a certain manner so they can be accessible any time. Moreover, the output and results of analyses are monitored by means of appropriate display. Finally, user may interrupt or reset the system via controller.

Before initiation of any task, the controller performs self test procedure to verify the proper functionality of all parts of the system including, motors, drivers, electronic circuits, power supply, processors, etc. Furthermore, controller checks the system during performance for possible fault and sends warning message to the user. As an example, if user set the limit of displacement 3 mm and set the speed of deformation 20 mm/s, the controller send a message for requesting reconfirmation of the parameters. Moreover, the controller checks the performance of the system during task and stops the mechanism in case of inappropriate consequences. For example, the first deformation speed is set 4 mm/s while the quality of the object is still unknown and no deformation has occurred after applying the force up to half of the limit range, the controller would stop the procedure and send user a message of error. 

1- A method of real time characterization of soft materials and biological tissues based on nonlinear properties comprising: deforming the target object in low speed rate by a compressive force applied by a mechanism and performing measurements during deformation with respect to time, analyzing the results of measurements of first deformation through nonlinear analyses, repeating the deformation with high deformation speed once more, analyzing the results of measurements of second deformation through nonlinear analyses, and monitoring the results of analyses in terms of nonlinear mechanical properties. 2- The method of claim 1, wherein said analysis of viscoelastic and plastic materials is based on the model of interactive combination of two elements of time independent and time dependent. 3- The method of claim 1, wherein said analyses are performed through nonlinear approach for hyperelasticity. 4- The method of claim 1, wherein said analyses are performed through nonlinear approach for viscoelasticity. 5- The method of claim 1, wherein said the analysis of first deformation determines nonlinear elastic modulus of hyperelastic or elastic element of the object. 6- The method of claim 1, wherein said analysis of second deformation determines dissipation at the speed deformation if exists, otherwise confirms the time independency of the object. 7- The method of claim 1, wherein said characterization of dissipation function of viscoelastic objects with respect to deformation speed requires, at least, two more deformations with two other deformation speeds. 8- The method of claim 1, wherein said deformation and measurement are performed by means of a mechanism. 9- The method of claim 1 is performed by a system mainly comprising: an analyzer, certain mechanisms, and a controller. wherein system performs real time characterization of soft materials and biological tissues based on nonlinear properties 10- The system of claim 9, wherein system includes any other devices required for performing the method of claim 1 beside the main parts of claim
 9. 11- The use of system of claim 9 in part or whole in any device. 12- The system of claim 9, wherein any system which performs the method of claim
 1. 13- The mechanisms of claim 9, wherein any mechanism is one of, similar to or combination of SCM, GCM, RCM, PCM, GJM, PJM, RPM, FPM, PJM, SCM, PPM and SPM. 14- The mechanisms of claim 9, wherein any device performs the deformation and measurements of claim 1 similar to any of mechanism of claim
 13. 15- The use of any of mechanisms of claim 13 for characterization, tactile sensing of objects or any other measurements for interacting with objects. 16- The use of SPM of claim 13 or any device similar to it for determining the geometry of any kind of objects. 17- The mechanisms of claim 9, wherein any mechanism performs the deformation and measurements of claim
 1. 18- The analyzer of claim 9, wherein any kind of device performs the analyzing procedures required for any of mechanisms of claim
 9. 19- The analyzer of claim 9, wherein any kind of device performs the analyses of method of claim
 1. 20- The use of procedures of any analysis applied by analyzer of claim 9 for any mechanisms of claim
 9. 21- The controller of claim 9, wherein any kind of device performs the controls required for the system of claim
 9. 22- The controller of claim 9, wherein any kind of device performs the controls required for one of, similar to, or combination of the mechanisms of claim
 13. 23- The use of system of claim 9, wherein said system performs characterization according to the method of claim 1 by tactile sensing. 24- The system of claim 9, wherein said endoscopic tools perform characterization of method of claim
 1. 25- The system of claim 9, wherein said a robot performs characterization of method of claim
 1. 26- The use of the method of claim 1 in any software, hardware or any manual procedure. 27- The use of the method of claim 1 in order to perform diagnostics of disorders of biological tissues. 28- The use of any one of parts of the method of claim 1 for characterization of soft materials and biological tissues. 29- The nonlinear approach of any of claims 3 or 4, wherein said the nonlinear approach is based on incremental nonlinear approach. 30- The system of claim 9, wherein said the system performs the method of claim 1 disregard of geometry, accessible surfaces and deformation condition of objects. 31- The method of claim 1, wherein said two deformations with two deformation speeds; one in the range of HSDL and one higher than HDSL are sufficient for complete characterization of elastic, hyperelastic and plastic materials, and are sufficient for characterization of viscoelastic material in some extend. 32- The use of any one of preceding claims, wherein said the object is soft material or biological tissue. 33- The use of any one of preceding claims, wherein said characterization is tactile sensing. 34- The use of any one of preceding claims; wherein said soft material is elastic, hyperelastic, plastic and viscoelastic material, or combination of them. 